Boat-propeller.



C. H. SAWYER. BOAT PROPELLBR.

APPLICATION FILED MAR. 15. 1913.

Patented May .26, 1914.

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. VV/TNEssss BY H15 ATTDRNEYS @Mv/Lm To all whom t may concern UNITED STATES PATENT OFFICE.

CHARLES H. SAWYER, OF KIN'NEAPOLIS, MINNESOTA.

BOAT-rnoPELLEn.

Speeication of Letters. 1ateiit.

Patented May 26,1914.

Application med Haren 15,- isis. seriai'iro. 754,625.

Be it known that I, CHARLES H. SAWYER, a citizen of the United States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Boat- Propellers; and I do hereby declare the following to be a full,`clear, and exact description of the invention, such as will enable.

others skilled in the art to which it apper-j tains to make and Ause the Same'.

My invention has for its object to improvey the construction of boat rop'ell'ers .of the well known vscrew or spira blade type, with aviewf obtaining greater propelling efficiency from the propeller. 1 y

It is a well known fact that when a screw propeller is rotated at high speed, a partial i vacuum is produced .just `in front ofthe propeller and just immediately at the rear of the'stern ofthe boat. This vpartialvacuum produces a back suction on the boat and decreases vthe eiiciency of the propeller. By

my invention, Ixprovide means for supplying air at the point where there is a tenden cy to produce the vacuum, and thereby relieve the boat from back pressure or suction and increasethe eiciency ofthe propeller.v In fact,` by vthus supplying air and destroying the-partial vacuumwhich would otherwise be produced, I am able to run the propeller wheel efficiently at a much higher speed than would otherwisebe possible.

In the accompanying ydrawings which illustrate the invention, like characters indicate-,like parts. throughout the several views.

Referring to the drawings, Figure 1 is a perspective View with some parts broken away, showing a boat ywith my improved propeller applied thereto; Fig. 2 is a detail in section-on the line wz :v2 on Fig. 1; Fig.

3 is asectioii taken on the line www on Fig. 1; and Fig. 4 is a section taken on the line m4 m* on Fig. 1.

The boat hull is indicated by the 'numeral 1, the lnumeral 2 indicates `a tubular propeller shaft, and the numeral 3 indicates the screw ropeller which is secured to the rear end of) the said shaft. This propeller has substantially standard. general outlines, but in accordance with my invention, its hub and blades are formed hollow, as indicated at' 7, and the blades of the propellerV on l their front-sides are formed with a multi-- plicity of air discharge passages 8.

The front end of the propeller shaft 2 is connected by a hollow sleeve 4, to the engine drivenshaft 9. The said sleeve 4 is formed wlth a plurality of air int-ake ports 5 that comn'iunicz'ite with the interior chamber of the sleeve 4, and hence, with the interior of the tubular shaft 2. lVitliin the sleeve 4 is a check valve 6 which freely opens topcr- .Y f

mit air to move from the ports 5 through the shaft 2 to the chamber 7 of the propeller.

This valve 6, however, will close and prevent j water from -iowing through the propeller shaft and into the boat. The numeral 10 indicates a scoop-like cup secured to the .sleeve 4' adjacent to the air ports 5 and serves, when the' propeller shaft is rotated in the direction of the arrows on Figs. l and 2, to assist in forcing air through the said discharged'through the air Vports the lfront faces of the saidpropeller blades. In.

this way, thepartial vacuum will bey either 4preventedjor reduced to a minimum. It

must, therefore be admitted that by thus destroying thevacuum in the backward suction at the rear of the boat, the operative eliiciency of the propeller is increased and it is made possible to efficiently' run the propeller ate. much-higher., speed than'is possible with a propeller constructed in the usual way. i

WhatIclaim is: i a

A propeller having a hollow shaft, hollow blades and air discharge ports' in the front facesbf saidl blades, said. propeller vshaft having-an air intake port and a check valve for preventing'the iow of Water from said prope lerto said air intake port.

In testimony whereof I laffix my vsignature l in presence of two witnesses,

CHARLES H, SAWYER. 4 Witnesses: i

HARRY D. KILGORE, F. D.v MERCHANT. 

